1. Field of the Invention
The present invention relates to a novel anisotropically conductive sheet, particularly, relates to a novel anisotropically conductive sheet useful for testing semiconductor devises such as semiconductor integrated circuits, simply called as ‘IC’ hereinafter, to inspect their electrical properties and relates to an apparatus for testing the semiconductor devices including a novel electrical interface using the anisotropically conductive sheet.
2. Description of the Related Art
Up until now, there have been proposed a wide variety of conventional electrically conductive sheets or films having an electrical conductivity only in thickness direction thereof, which is applied to an electrical test of a semiconductor devise.
In order to test electrical properties of a semiconductor device such as IC, terminals of the semiconductor device shall be connected electrically with electrodes of test circuit. However, semiconductor devices have various own constructions each by each and it is necessary to use appropriate means for assuring electrical connections between terminals of the semiconductor device and electrodes of the test circuit.
As one of such connecting means, an anisotropically conductive film is proposed in Japanese published patent application Kokai H07-140480A. The anisotropically conductive film comprises a composition in which conductive fine particles are dispersed in an insulating adhesive material.
At test stage of a semiconductor device, the anisotropically conductive film is laid between terminals of the semiconductor device and electrodes of test circuit and then compresses the semiconductor device toward the circuit of tester through the anisotropically conductive film to connect electrically the both.
Most of recently developed semiconductor devices, for example IC, are higher integrated and, therefore, the semiconductor devices becomes to high temperature, for example above 100° C., at test stage due to electric currents given to the semiconductor devices. In order to meet such high temperature, an anisotropically conductive film made of heat resistant materials is proposed. However, vibrations of the film take place by an outside pressure and static electricity is generated on the film during the test procedure. These problems cause difficulties to obtain exact test results.
Furthermore, when a semiconductor device to be inspected is pressed down to test circuit through the anisotropically conductive film, the film often adheres to the semiconductor device and/or the circuit board, for a vacuum space is formed between the semiconductor device and the circuit board by such pressing down. Thus, the film is occasionally damaged when the semiconductor device and the films are removed respectively from the circuit board after the test is finished.
For avoiding such drawbacks, an anisotropically conductive sheet has been suggested in Japanese published patent application Kokai H09-35789A. The anisotropically conductive sheet comprises an insulating material composed of silicone rubber and an electrically conductive material existing in the insulating material.
As the anisotropically conductive sheet has an adequate thickness, any vibration or adherence of the sheet does not appear. However, an oily material oozes out from the insulating material during the test, because the insulating material of the conductive sheet is made of silicone rubber. The oily material may pollute the semiconductor device and the circuit board of tester and it may bring troubles on a normal test. Since the oozing out of the oily material is increased at higher temperature, this anisotropically conductive sheet is unsuitable to apply for testing highly integrated IC, which rises in temperature during the test.
Furthermore, as the above anisotropically conductive sheet comprises a conventional conductive material, such as a conductive material having a ball-like shape, the ball-like conductive material may be deformed and damaged when a semiconductor device is pressed down toward the circuit board of tester through the anisotropically conductive sheet.